1. Field of the Invention
The present invention generally relates to an apparatus and method for positioning control; in particular, to an apparatus and method for positioning control which is used to control the moving and positioning of a controlled device in accordance with the comparison of a moving command and a dead point default value.
2. Description of Related Art
Referring to FIG. 1, a block diagram of a prior art control system is shown. In such a conventional control system, there comprise a man-machine interaction or a commander 10 (MMI-C 10), a control driving circuit 12 and a controlled device 14. The control driving circuit 12 receives the command SD sent from the MMI-C 10 and further outputs a control signal SC to the controlled device 14 according to the command SD. The controlled device 14 is controlled by the control signal SC and acts accordingly, and sends a feedback signal SF back to the control driving circuit 12, in order to provide control for the driving circuit 12 to perform closed-loop control. In addition, the control driving circuit 12 may also send the control status back to the MMI-C 10, so as to allow the user to check the status of the control system.
In conjunction with FIG. 1, now refer to FIG. 2, in which a diagram of prior art slider moving control is shown. The moving control of the slider 20 uses the above-mentioned prior art control system. The MMI-C 10 issues a forward command SD to the control driving circuit 12, enabling the control driving circuit 12 to drive the controlled device 14 installed in the slider 20 for driving the slider 20 to move forward. At the same time, the controlled device 14 sends a feedback signal SF to the control driving circuit 12. In this way, the control driving circuit 12 may controls the forward moving of the slider 20 via the classic closed-loop controller method.
As the slider 20 moves to a dead point, the top pin 202 on the slider 20 will trigger a feedback device 24. It should be noted, the term dead points from structure engineering are notches used to lock the position, when used in terms of mechanical control system, it serves similar meaning, and refers to a defined geometric point. At this time, the feedback device 24 sends a dead point feedback signal ST to the control driving circuit 12, so as to inform the control driving circuit 12 to perform braking action or reset, which would prevent the slider 20 from impacting the critical plane 22 and allowing for the general positioning of the slider 20. The approach of control may compensate for the positioning of the slider 20 from the influences caused by factors such as wearing, dusts, airflow, vibrations, thus allowing normal operation.
However, as the machining technologies advance, more and more designs of part/component or combination thereof needs to meet the requirements of high precision, low error and small size; meanwhile, the moving and positioning of the aforementioned slider 20 are required to satisfy the said requirements as well.
Hence, when the moving condition of the controlled device 14 being driven enters into the micro cosmic or near-field scope, the volume of the feedback device 24 is often too big, thus implementation becomes impossible. Besides, the feedback device 24 may generate error in responsiveness due to factors of wearing, dusts or machining and so on, resulting in the existence of a spacing gap between the braking position of the slider 20 and the critical plane 22, wherein the gap would not effectively approach zero.
Meanwhile, if the feedback device 24 is removed, the spacing gap between the braking position of the slider 20 and the critical plane 22 may still be impossible to approach zero due to the factor of variation in the surface of the critical plane 22; more seriously, after the integration on the spacing gap by the integration processor (not shown) in the control driving circuit 12, it will generate huge driving force to drive forward the slider 20, causing the controlled device 14 to be subject to tremendous invalid power, and thus can even be damaged.